Grégory Breton, writing for Panthera, said he’s been searching for the cats in the Sahara since 2013. It took his group a full nine days on the first expedition before they even saw a single cat.

It took them three year and five expeditions before they were able to capture them in detail.

“They barely leave any visible pugmarks, they don’t leave behind remains of their prey, and their vocalizations are quiet. They move stealthily at dusk, night, and dawn, they’re good at hiding, and their fur provides perfect camouflage when they want to vanish from observers and threats,” Breton wrote.

Add to that, sand cats tend to live in tough wilderness, places where researchers must endure high temperatures and the occasional sandstorm.

Because the animal is so hard to track, assessing populations has been difficult, according to Mother Nature Network. The species is believed to be extinct in Israel, for example, though a litter was born at the Zoological Center of Tel Aviv in 2012.

“Ours has been the most extensive research on this species, and it will surely help to protect it,” Breton wrote.